Vicinal diols are useful as components in the production of polyesters and polyurethanes as well as in the cosmetic and pharmaceutical industry.
They are produced, inter alia, by saponification of their corresponding epoxides. This saponification is catalyzed both by the addition of acids (cf. for example the state of the art in U.S. Pat. No. 3,576,890) and of alkalis (cf. for example DE-OS No. 17 93 247; DE-OS No. 22 03 806) and of salts of aliphatic mono or polycarboxylic acids (DE-OS No. 22 56 907) as well as primary, secondary or tertiary amine salts or ammonium salts (EP-OS No. 0 025 961).
It is also known that the acid acting as catalyst can be produced by means of the addition of esters of lower carboxylic acids and their hydrolysis to alcohol and acids (U.S. Pat. No. 3,576,890).
The saponification can be performed in a purely aqueous medium or in the presence of solubilizing agents such as water-soluble ketones or cyclic ethers (DE-OS No. 22 56 907). The last-named patent explains that difficulties arose in a purely aqueous hydrolysis of epoxides without the presence of solubilizing agents, if one did not use ethylene oxide but rather high molecular weight water-insoluble epoxides. The result was long reaction times, moderate yields and poor selectivity.
The difficulties were naturally especially great in the saponification of epoxides or epoxide cuts which contained 8 to 30 carbon atoms due to their poor water solubility. Therefore, the discontinuous saponification of long-chain epoxides to the corresponding diols was performed according to European patent specification EU-PS No. 25 961 using special catalysts, namely ammonium salts of organic or inorganic acids. The amount of catalysts in relation to the epoxide used was high; in spite of the use of an autoclave, the reaction times were around 4 to 6 hours generally and the yields were only moderate.